Method of manufacturing ketenes



July 13, 1937. 'K."T. STEIK I 2,036,532

METH OD OF MANUFACTURING KETENES Filed Aug. '29, 19:50

Patented July I 13, 1937 METHOD OF MANUFACTURING KETENES Karl '1. Steik, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application August 29, 1930, Serial No. 478,618

8 Claims. (Cl. 260-123) The present invention relates to improvements in the manufacture of organic compounds of the type of acetic ketene (CHzzCO) and its homoogs.

The invention will be fully understoodfrom the following description, read in connection with the accompanying drawing, in which Fig. 1 is a diagrammatic view in elevation ofequipment suitable for practicing the method;

Fig. 2 is a modification of the ketene recovery stage shown in Fig. 1; and

Fig. 3 is another modified form.

It will be assumed, for facilitating the description, that acetic ketene is to be made from isopropyl alcohol. Referring first to Fig. 1, reference numeral l denotes a long reactor or retort, mounted on a support 2. The two ends of the reactor, forming ,the two extremes of the reaction zone, are designated 3 and 4. A pipe 5 constantially all higher-boiling compounds that may be formed by side reactions. A temperature of about 60 C. is satisfactory. Provision for rapid cooling to check any tendency to after-reaction, may be provided, for example as described in 5 connection with Fig. 3. The condensate from separator [0 may be passed, if desired, through line H into the isopropyl alcohol inlet line 5. The separator may be of any suitable form, for example a bubble cap tower or the like.

Ketene, unreacted acetone, sometimes with traces of water formed by side reactions, and combined or uncombined, pass from separator I0 through a'line it! into a second separator l3. This is held at a temperature at which acetone is condensed and ketene passes over. Since ketene boils at about minus 56 C. and acetone at plus 56 C., a temperature separation is possible, notwithstanding the solubility of ketene in acetone.

2O veys preheated isopropyl alcohol vapor into the Ketene flows through line 'H to a recovery drum lower temperature section 3 of the reactor. An- 0r tower 5, preferably containing bubble cap hydrous alcohol is used unless aqueous addition plates 01' the like, nd Wh h has valved Vapor products are desired, as described further on. and liquid draw-011' lines andfib- Products Section 3 is packed with a dehydrogenating cataowing t rough line 0 y be discharged lyst, preferably reduced copper, granular zinc t roug a valv Vent line '56 to a eat 25 oxid, or brass turnings. Air is substantially ex tank or tanks I5d. The product from this tank cluded. Heating means 6 are provided to maino ta ks may be tu e to the Sy through tain section 3 at about 400 to 625 c. The isoa line we, i which there is a vent 1- Dropyl alcohol may be, preheated in a coil 1, if Dr m l5 m y be harged with cellulo desired. pended in acetic acid or-other suitable liquid, if 30 .The reactor is heated in such a manner that the temperature of the gases and vapors therein is progressively increased, say from 400 to 625 C. at the inlet end to about 625 or 850 C. at the outlet end. The reaction tube should be of copper, brass, or similar metal, or it may consist of a steel tube lined with copper, brass, or the like.

Decomposition of. the isopropyl alcohol to acetone and hydrogen takes place in the inlet portion 3 of the reactor. The outlet portion of the reactor, where decomposition of some of the acetone to ketene and methane occurs may be packed with quartz beads, or the like. It is heated by any suitable means 8.

of acetone but sufiiciently low to condense subit is desired to prepare cellulose acetate, or the drum may be charged with anhydrous alcohols for the manufacture of esters, such as acetates, etc. Ketene is a highly reactive compound and tends to decompose or polymerize on standing. 35 Hence it is desirable to cause it to react as soon as possible after its formation. Due to the high reactivity of ketene, the number of possible reactions is large. Besides those listed above, the following may bementioned: 40

Reaction with ammonia to form acetamide.

Reaction with water to form acetic acid, either directly or as a means of concentrating dilute acetic acid.

h pressure in the reactionzone may be sub- Reaction with the water content of higher or- 45 stantially atmospheric, but superatmospheric or g c ac to fortify their Solutionssubatmospheric pressures are not precluded. Reaction with hydrogen to form acetaldehy'de. The rate of flow is dependent on the tempera- Reaction with unsaturated hydrocarbons to ture and is to be determined by practical considform addition products.

erations in connection with recycling, as subse- Reaction with aniline to give acetanilide. 50

quently described. Reaction with hydrochloric acid to yield acetyl The reaction products discharge through line chlorid.

9 and cooler 9a into acooled separator l0 main- Reaction with various impurities of hydrocartained at a temperature above the boiling point bon oils, especially sulfur compounds such as mercaptans. 55

. 13 through line IS the introduced at the middle I -genation and acetaldehyde may be produced preliminary removal of acetone and other components of the reaction mixture.- Instead of a single reaction vessel for the recovery of ketene, any desired number may be provided to insure substantially complete reaction.

The liquid products discharged from separator or towards the outlet portion of the reactor. A preheater ll may be provided in this line. The undecomposed alcohol in these products may-be separated, from the other constituents andsent through by-pass l6b (valve l6c being opened) into the lower temperature zone of the reactor.

The extent of reaction in the outlet portion (l) of the reactor should be controlled withindesirable to hold the conversion-per pass belowbased on the total quantity of acetone entering the reaction zone. About 5 to 10% conversion per pass in many instances gives the greatest over-all efiicienoy for the cyclic operation. The degree of dilution with unconverted acetone, or the like, may be regulated as desired to meet special conditions.

Valves 5a, 9a, Ha, Ha, I la, and 16a are pro vided in the lines bearing the corresponding numbers, for the control of the system. The temperatures of the inlet and outlet portions of the reactor are determined by pyi'ometers l8 and 59. I i

In the alternative form shown in Fig. 2, a single separating drum or tower 20. is provided, corresponding to separator In of Fig. l. Ketene and. acetone are discharged through line 2| from drum 29 into a ketene recovery drum 22 charged with cellulose or other reactive substances. Acetone and unreacted ketene passing through line.

23 are sent back tothe reactor through line ll (Fig. 1).

In the form of the invention shown in. Fig. 3 I provide for the rapid cooling of-the reaction product. This is preferably accomplished by.-

injecting into the line 9, which carries the reaction product, a cooling agent which may be the condensate formed from the reaction product. Line Q discharges into the middle portion of a separator tower 2B, which may be provided with the usual bell cap plates or the like. A line 25,

in which there is a pump 26 withdraws liquid from the bottom of 24. A cooling coil 27 is inserted in line 25. This line discharges into line 9 and the mixed liquids from the two lines pass into the tower together. Valve 28 is provided in line 9 and maybe used to control the pressure.

A float control mechanism 29 holds the desired liquid level in tower'24. Surplus liquid is dischargedthrough line 39.

"ti into the recovery apparatus 32.

densate formed in tower 26 comprises acetone and various other constituents of the reaition The conmixture'which are liquids under the conditions of operation, together with some dissolved .ketene.

from the tower to the reaction zone.

The invention has been described primarily in connection with acetic ketene but it is applicable also to higher ketenes such as those which are derived from butyl and amyl alcohols and the like, or other ketenizable alcohols, especially the lower secondary alcohols. 'Ketene may be produced from 'acetaldehyde by limited dehydrofrqm ethyl alcohol. Accordingly I may substitute described. Instead of anhydrous isopropyl alcohol, the ordinary commercial isopropyl alcohol containing about 12% of water may be used. Some of the ketene will react with the-water to form acetic acid or acetic anhydride. When the 1 manufacture of these compounds is the end in" view it is d e sirable to use the aqueous commercial alcohol and the yield of acetic anhydride, or acetic acid may be controlled by'adding water.

One of the valuable uses of the present method is in the preparation of estersT-It will be observed that an ester may be prepared from an alcohol, using the latter as the only source material; For example, in the operation of the method in connection with an oil refinery, isopropyl alcohol may be manufactured in quantity fromthe refinery gases.

A ,portion of the alcohol so produced is decomposed to ketene and this is reacted either as such, or through acetic anhydride or acetic acid as an intermediate stage, with another portion of the isopropyl. al-

cohol. The reaction between the alcohol and ketene is very easily effected by merely bubbling It is'desirable to return surplus liquid,

the latter through the alcohol, preferably in a series of reaction vessel s. A very pure and com-.- pletely esterified material may be obtained from the first drums of the series.

While we prefer to-react the ketene with alcohol in a separate stage for the manufacture of esters, it is possible to form them by reaction of ketene with undecomposed alcohol passing-through the conversion tubes.

When converting a ketenizable alcohol such as isopropyl alcohol to acetone, a high yield of acetone .is obtained and only a small percentage of the isopropyl alcohol passes on into the higher temperature zone in which ketene is produced. In this zone residual isopropyl alcohol is decomposed at least in part to propylene. Ordinarily, there is not enough of this hydrocarbon to warrant recovery, but in the manufacture of higher ketenes where the conversion of alcohol in the initial stage is not so good, it is desirable to recover the olefins formed in the second stage. These may be sulfated and hydrolyzed .to re- 7 form the alcohol for return to the system. Equipment for carrying this out is shown diagrammatically in Fig. 1 (i522, 85d and 55a).

' The particular form of reactor shown is merely diagrammatic and any suitable type may be used. The waste'gases maybe burned to heat the reactors. a

By the process described it is possible to obtain commercial yields of ketene and related products directly from materials such as alcohol. The invention includes the employment of ketenizable alcohols whether. these are of the secondary type, keteni'zing through the ketone (or enolic) route, or otherwise. I have found that operation under the conditions defined herein is practical and advantageous notwithstanding the presence of hydrogen and other reaction products resulting from the initial decomposition of the alcohol. I

The foregoing description is illustrative oi preferred embodiments of the invention but various changes and alternative arrangements may be made within the scope of the appended claims,

in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits. 4

I claim:

1. The method of manufacturing ketenes which comprises subjecting organic compounds selected from the group consisting of alcohols and aldehydes and capable of producing ketenes by dehydrogenation and heat, to progressively higher temperatures in stages, without removing 3. Process according to claim 2, in which a dehydrogenation catalyst is present in the first stage.

4. Process according to claim 2, carried out in a reaction chamber at least lined with a nonierrous metal having a positive catalytic influence on the reaction.

5. The method of manufacturing ketenes, which comprises subjecting organic compounds capable of producing ketenes by dehydrogenation version of the ketones formed in the first stage into ketenes is maintained substantially below 50%, without removing intermediate reaction products between stages, and recycling part of the reaction products, other than ketenes, through the second or ketenizing zone.

6. The method of manufacturing ketenes, which comprises subjecting secondary alcohols to progressively higher temperatures in stages, without removing intermediate reaction products between stages.

7. Method. according to claim 6, in which isopropyl alcohol is treated and acetic ketene is produced, the temperature in the last stage being maintained between the approximate limits of 625 and 850 C.

8. Method according to claim 6, in which olefin by-products are recovered by treatment with sulnu'ic acid and subsequent hydrolysis, and they resulting alcohol recycled through the keteneiorming process.

KARL T. BTEIK, 

